Fraunhofer Institute for Microstructure of Materials and Systems IMWSThe fiber-reinforced composite industry is booming – but the production of UD tapes generates up to 15 percent of the material as edge trim waste. The Fraunhofer Institute for Microstructure of Materials and Systems IMWS aims to change this in collaboration with partners: The “ReTape” research project is developing a process to feed this edge trim directly back into the production process. Through multi-stage comminution, gravimetric dosing, and incorporation into the compounding extruder, the edge strips are to be converted into short-fiber-reinforced compounds for injection molding.
Fiber-reinforced plastics (FRP) enable significant weight reductions while maintaining high strength and stiffness. Unidirectional continuous-fiber-reinforced semi-finished products, known as UD tapes, offer particularly great potential for such lightweight construction solutions. However, during their production, so-called edge trimmings are generated at the edges of the wide tapes. These narrow strips contain valuable fiber material and high-quality polymers, yet they have so far been disposed of as waste or, at best, reused in low-grade applications.
Up to 15 percent edge-trimming waste to date
“In industrial practice, up to 15 percent of the material is generated as edge-trimming waste during UD tape production. This is not only economically questionable but also contradicts the industry’s sustainability goals,” explains Benjamin Tillner, project manager at Fraunhofer IMWS. “We see significant potential here to conserve resources and reduce production costs through intelligent recycling processes.” Industries such as the automotive sector, aviation, the wind energy sector, and shipbuilding – which are seeking new approaches to more sustainable production – could benefit, especially in light of rising prices for high-quality raw materials such as glass and carbon fibers.
Project goal: direct recycling of UD tape trimmings in the production process
In the “ReTape” research project, Kurt Seume Spezialmaschinenbau GmbH, Ematik GmbH, and Fraunhofer IMWS therefore aim to develop a process for the inline recycling of UD tape edge trimmings during the ongoing production process. The cut edge strips are to serve directly as raw material for fiber-reinforced injection molding compounds with precisely defined fiber content.
The central question here is how the edge trimmings can be mechanically processed, metered, and uniformly reintroduced into the manufacturing process without compromising the quality of the resulting products. The challenge lies in maintaining the fiber length and orientation, ensuring homogeneous distribution within the polymer, and adjusting the process parameters so that a constant fiber mass fraction in the compound can be guaranteed.
“We’re not interested in downcycling – that is, converting materials into lower-quality products. We want to create closed-loop material cycles in which the quality of the raw material is preserved,” Tillner emphasizes. “That requires a deep understanding of material properties and precise process engineering.”
Defined fiber fractions instead of inhomogeneous shredder fractions
Previous approaches to recycling FRP waste have focused on energy recovery through incineration or mechanical recycling into fiber granules or regrind with variable fiber content. The “ReTape” project takes a significant step further. The edge sections are processed into high-quality injection molding compounds using the process technology developed in the project and are intended to contain a constant fiber mass fraction. The technological solution is designed to function as a supplementary system for existing extrusion and compounding systems, which can be adapted to existing equipment. Furthermore, the tape edge trimmings represent only the first stage of evolution and are intended to be supplemented by any intermediate products and semi-finished goods generated during UD tape processing. This approach aims to enable the direct recycling of cost- and energy-intensive raw materials and to eliminate the need for additional recycling facilities.
The edge trimmings are first analyzed in detail, for example with regard to fiber orientation and mechanical properties. Based on this, the partners are developing the shredding and dosing system, which must ensure a uniform feed to prevent blockages or fluctuations in the process. To this end, appropriate control and automation technology for the extrusion process is being developed. The manufactured materials are then comprehensively characterized, and the structure-property relationships are investigated in order to derive recommendations for robust process parameters.
The Fraunhofer IMWS contributes its expertise in process development, the comprehensive characterization of recycled materials, and the development of quality control methods. Modern testing and simulation techniques are used in this process. At the Fraunhofer Pilot Plant Center for Polymer Synthesis and Polymer Processing (PAZ) in Schkopau, the research results can be tested directly on industry-scale equipment to support a rapid transition to series production.
(May 5, 2026)